Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

813
FXUS63 KLOT 091107
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
607 AM CDT Mon Mar 9 2026

.KEY MESSAGES...

- Severe thunderstorms Tuesday afternoon and evening, with the
  potential for very large hail, damaging winds and tornadoes.

- Potential for heavy rain and localized flash flooding Tuesday
  afternoon into Wednesday morning.

- Possible very strong winds (40+ mph) Thursday night/Friday.

&&

.DISCUSSION...
Issued at 220 AM CDT Mon Mar 9 2026

The primary forecast concern is the severe weather potential
Tuesday afternoon into Tuesday evening.

For today, high temps are expected to warm well into the lower
70s which if these materialize will be new records for today for
much of the area. Southwest winds will remain breezy, gusting
into the 25 to 30 mph range at times. The models continue to
show a weak disturbance lifting northeast across the Ohio Valley
this evening with a chance for a few showers/sprinkles across
the far southeast cwa. There has been fair agreement with this
for several model runs and added slight chance pops for this
evening for the far southeast cwa.

A cold front will be moving south across the western Great Lakes
this evening and the models are now showing this front entering
northern IL after midnight tonight, possibly as far south as the
I-88 corridor by daybreak Tuesday morning. Most of the cams
along with the NAM/GFS have this front continuing south to the
I-80 corridor by Tuesday afternoon. There will be a large temp
gradient along this boundary with temps falling through the 50s
and possibly into the 40s behind the front, while temps south of
the boundary will be in the 70s. Have trended colder with temps
for Tuesday with this further south progression of the front.
However, temps will likely needed to be lowered further if these
trends with the cold front continue.

As low level moisture slowly increases later today into tonight,
the models are showing fog developing over Lake Michigan and
have added patchy fog overnight into Tuesday. This fog will
likely become dense over the water and some of this fog may move
inland or develop along/ahead of the front as it moves south on
Tuesday, with fog mention possibly being needed over land with
later forecasts.

Low pressure will develop over the Plains Tuesday and move
northeast across the local area Tuesday night. As it does,
scattered thunderstorms will develop during the mid/late
afternoon and continue through Tuesday evening, slowly moving
east southeast Tuesday night. The SPC Day 2 outlook has
expanded the enhanced (level 3) severe risk northeast through
roughly the I-88 corridor. All modes of severe weather will be
possible along and south of the boundary. North of the
boundary, very large hail will still be possible with elevated
thunderstorms. The end time of the severe thunderstorm threat
is somewhat uncertain but may continue through late evening
for much of the area and into the early overnight hours (early
Wednesday morning) for the far southeast cwa. With this enhanced
severe risk, have included severe mention in the grids/zfp for
late Tuesday afternoon and then all of Tuesday evening.

Heavy rain is also expected with these thunderstorms and there
is the potential for training thunderstorms, especially across
the southern half or so of the area Tuesday night into Wednesday
morning. Wherever this materializes, there will be the potential
for localized flash flooding. Rain will likely be ongoing
Wednesday morning and may continue through early afternoon as it
ends from northwest to southeast across the area. Colder air
will be spreading across the region and there may be a mix with
or change to light snow, but not expecting any accumulation at
this time.

Another strong storm system is expected to move across the
northern Plains and upper Midwest Thursday night and across the
northern Great Lakes region Friday. Strong southerly winds will
develop across the area Thursday evening ahead of a trailing
cold front from this storm system which will move across the
area Friday morning. Winds will shift west/northwest behind the
front and continue to be strong on Friday. Still several days
away but given the track and strength of this system, wind gusts
40+ mph are possible. The local area appears to be on the south
edge of the precipitation, which could end as a rain/snow mix
Friday morning.

No significant changes to the model trends for this weekend into
early next week. It still appears active with a system moving
across the area this weekend with the potential for a rain/snow
mix then a pattern shift to colder early next week with perhaps
additional snow chances. cms

&&

.AVIATION /12Z TAFS THROUGH 18Z TUESDAY/...
Issued at 607 AM CDT Mon Mar 9 2026

Marginal LLWS will linger at the outlying TAF sites early this
morning. Otherwise, south-southwesterly breezes will continue
today with periodic gusts around 25 kts. Gusts will ease this
evening.

Low-level moisture will surge northward across the region
tonight into early Tuesday morning. With this moisture will come
the potential for MVFR/IFR cigs and vsbys. At this time, it
remains a bit unclear just how far west any low cigs will
develop. Have introduced a TEMPO group for near-IFR cigs at GYY
but have withheld a lower mention at the other TAF sites
through 12z Tuesday due to low confidence. At DPA, ORD, and MDW,
have added a mention of some BR, with some potential that lower
conditions may be needed in future issuances.

Eventually, a shallow cold front will push off the lake Tuesday
morning resulting in a N/NNE wind shift. Some variability in the
specific timing remains, but have added a wind shift at ORD at
12z and an hour later at MDW. IFR cigs should develop in the
wake of the front, along with the potential for IFR vsbys.

Carlaw

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory until 10 AM CDT this morning for the IL
     and IN nearshore waters.

&&

$$

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